A magnetoelastic sensor is based on the inverse magnetostrictive effect, that is to say the effect according to which ferromagnetic materials experience a change in magnetic permeability if mechanical stresses occur. Since mechanical stresses are induced by tensile forces and compressive forces as well as by torsion, the inverse magnetostrictive effect can be used for measuring force and/or torque, and can therefore be employed in a versatile way.
Measurement heads for measuring the inverse magnetostrictive effect comprise a transmission coil or exciter coil with which a magnetic field is induced in the ferromagnetic layer. In this context, a response signal having a magnetic flux density that depends on the permeability of the layer is generated in the layer. The permeability is determined in turn by the mechanical stresses present in the layer. The magnetic flux density of the response signal determines the strength of the current induced in the reception coil owing to the magnetic flux density penetrating it. The mechanical stresses in the ferromagnetic layer can therefore be calculated on the basis of the strength of the current.
However, owing to fabrication tolerances the reception coils, and therefore the measurement heads, have limited reproducibility in the manufacture and limited accuracy during measurement.